alien.py

import pygame
from pygame.sprite import Sprite

class Alien(Sprite):
    """表示单个外星人的类"""
    def __init__(self, ai_game):
        """初始化外星人，设置位置参数

        Args:
            ai_game (_type_): _description_
        """
        super().__init__()
        self.screen = ai_game.screen
        self.settings = ai_game.settings

        # 加载外星人
        self.image = pygame.image.load('images/alien.png')
        self.rect = self.image.get_rect()

        self.rect.x = self.rect.width
        self.rect.y = self.rect.height

        self.x = float(self.rect.x)

    def check_edges(self):
        """检查外星触碰边缘

        Returns:
            _type_: 判断alien rect的左侧是否大于屏幕rect左侧值 条件成立时返回True.
        """
        screen_rect = self.screen.get_rect()
        if self.rect.right >= screen_rect.right or self.rect.left <=0:
            return True
        
    def update(self):
        self.x += (self.settings.alien_speed * self.settings.fleet_direction)
        self.rect.x = self.x